1. Field of the Invention
The present invention relates to a semiconductor device having a standing structure of a semiconductor layer and a method of fabricating the same.
2. Description of the Background Art
Micro-optical benches with standing structure are realized by micro-machining technology using silicon. It is reported that resonant micro scanners for laser scanning display, movable micro reflectors, and scanning micro mirrors for external resonators of semiconductor lasers, for example, are fabricated using the micro-machining technology.
In the conventional micro-machining technology, a part of a laminated semiconductor layer is stripped by etching, the stripped part is slid to stand and is joined by a hinge, to form a standing structure. A mirror or the like standing at a predetermined angle is constructed on a substrate using the standing structure.
When the standing structure is produced by a semiconductor using the conventional micro-machining technology, however, wear occurs in sliding the stripped semiconductor layer. Further, sliding the semiconductor layer to a predetermined position requires manual operations or complex electrostatic engines. Therefore, the micro-machining technology is more complex and is inferior in workability.
An object of the present invention is to provide a semiconductor device capable of self-assemble during the fabrication process and of accurately controlling the angle and the position of each of members constituting a standing structure as well as being easily comprised of a semiconductor layer and a method of fabricating the same.
A semiconductor device according to an aspect of the present invention comprises a substrate, a first layer, a second layer, and a third layer in this order, the second layer including a stacked structure of a first semiconductor layer having a first lattice constant and a second semiconductor layer having a second lattice constant smaller than the first lattice constant, the third layer, the second layer and the first layer in a region surrounding a predetermined region of the third layer, excluding a partial region, being removed, the first layer in the predetermined region and the partial region being removed, and the second layer in the predetermined region being bent at the partial region.
In the semiconductor device, the third layer, the second layer and the first layer region in the region surrounding the redetermined region, excluding the partial, are removed, and the first layer in the predetermined region and the partial region are removed. Accordingly, the second layer in the predetermined region is in a released state while being linked to the surrounding region only in the partial region. Since the lattice constant of the first semiconductor layer in the second layer is larger than the lattice constant of the second semiconductor layer, strain based on the difference in the lattice constant is induced in the second layer. Consequently, the second layer is bent so as to relax the strain. As the second layer is bent, the third layer on the second layer stands at a predetermined angle to the substrate.
The second layer is automatically bent so as to relax the strain caused by the difference in the lattice constant between the first semiconductor layer and the second semiconductor layer, whereby the third layer stands on the substrate. Therefore, the angle of the third layer can be easily and accurately controlled by adjusting compositions and the thicknesses of the first semiconductor layer and the second semiconductor layer.
Consequently, a semiconductor device capable of accurately controlling the angle and the position of each of the members constituting the standing structure as well as being easily comprised of a semiconductor layer is realized.
The third layer in the partial region may be removed. Consequently, the second layer can be easily bent at the partial region.
The third layer may include a third semiconductor layer having a lattice constant approximately equal to that of the first semiconductor layer in the second layer. In the case, the third layer is prevented from being curved, thereby forming a flat third layer standing on the substrate.
The third layer may include a third semiconductor layer having a lattice constant different from that of the first semiconductor layer in the second layer. In the case, the third layer is curved, thereby forming a third layer in the shape of a cylindrical surface standing on the substrate.
The third layer on the second layer, in the predetermined region, bent at the partial region may have a flat surface. In the case, the flat third layer standing on the substrate is formed.
The third layer on the second layer, in the predetermined region, bent at the partial region may have a cylindrical surface. In this case, the third layer in the shape of a cylindrical surface standing on the substrate is formed.
The predetermined region may include a plurality of regions, the parts of the second layer respectively bent in the plurality of regions or the parts of the third layer on the parts of the second layer may be abutted against each other.
In this case, the plurality of parts of second layer or the plurality of parts of third layer are abutted against each other, whereby the angle of each of the parts of the third layer is defined. Accordingly, the angle of each of the parts of the third layer can be accurately set to a desired angle without precisely controlling the compositions and the thicknesses of the first semiconductor layer and the second semiconductor layer.
The third layer may include a reflective film. In this case, a mirror standing on the substrate can be constructed.
The first layer may be a release layer, the second layer may be a strain layer, and the third layer may include a component layer.
A semiconductor device according to another aspect of the present invention comprises a substrate, a first layer, a second layer, and a third layer in this order, the second layer including a stacked structure of a first semiconductor layer having a first lattice constant and a second semiconductor layer having a second lattice constant smaller than the first lattice constant, the third layer, the second layer and the first layer in regions respectively surrounding a plurality of predetermined regions of the third layer, excluding partial regions, being removed, the first layer in the plurality of predetermined regions and the respective partial regions being removed, and the second layer in the plurality of predetermined regions being bent at the respective partial regions.
In the semiconductor device, the third layer, the second layer and the first layer in the regions surrounding the plurality of predetermined regions, excluding the respective partial regions, are removed, and the first layer in the plurality of predetermined regions and the respective partial regions is removed. Accordingly, the parts of the second layer in the plurality of predetermined regions are in a released state while being linked to the surrounding regions only in the respective partial regions. Since the lattice constant of the first semiconductor layer in the second layer is larger than the lattice constant of the second semiconductor layer, strain based on the difference in the lattice constant is induced in the second layer. Consequently, the parts of the second layer are bent so as to relax the strain. As the parts of the second layer are bent, the parts of the third layer on the parts of the second layer stand at a predetermined angle to the substrate in the plurality of predetermined regions.
The parts of the second layers are automatically bent in the plurality of predetermined regions so as to relax the strain caused by the difference in the lattice constant between the first semiconductor layer and the second semiconductor layer, whereby the parts of the third layer stand on the substrate in the plurality of predetermined regions. Therefore, the angle of the parts of the third layer in the plurality of predetermined regions can be easily and accurately controlled by adjusting the compositions and the thicknesses of the first semiconductor layer and the second semiconductor layer.
Consequently, a semiconductor device capable of accurately controlling the angle and the position of each of members constituting the plurality of standing structures as well as being easily comprised of a semiconductor layer is realized.
The third layer in the respective partial regions may be removed. Consequently, the parts of the second layer can be easily bent in the partial regions.
The parts of the second layer, in the plurality of predetermined regions, bent at the respective partial regions or the parts of the third layer on the parts of the second layer may be abutted against each other.
In this case, the plurality of parts of the second layer or the plurality of parts of third layer are abutted against each other, whereby the angle of each of the parts of the third layer is defined. Accordingly, the angle of each of the parts of the third layer can be accurately set to a desired angle without precisely controlling the compositions and the thicknesses of the first semiconductor layer and the second semiconductor layer.
The parts of the second layer bent in at least one of the predetermined regions or the part of the third layer on the part of the second layer may be abutted against another part of the second layer or another part of the third layer.
In this case, at least one part of the second layer or third layer is abutted against another part of the second layer or another part of the third layer, whereby the angle of the part of the third layer is defined. Accordingly, the angle of the part of the third layer can be accurately set to a desired angle without precisely controlling the compositions and the thicknesses of the first semiconductor layer and the second semiconductor layer.
A method of fabricating a semiconductor device according to another aspect of the present invention comprises the steps of forming a first layer on a substrate; forming on the first layer a second layer including a stacked structure of a first semiconductor layer having a first lattice constant and a second semiconductor layer having a second lattice constant smaller than the first lattice constant; forming a third layer on the second layer; removing the third layer, the second layer and the first layer in a region surrounding a predetermined region of the third layer, excluding a partial region; and selectively removing the first layer in the predetermined region and the partial region, to bend at the partial region the second layer in the predetermined region.
According to the method of fabricating the semiconductor device, the third layer, the second layer and the first layer in the region surrounding the predetermined region, excluding the partial region, are removed, and the first layer in the predetermined region and the partial region is removed. Accordingly, the second layer in the predetermined region is in a released state while being linked to the surrounding region only in the partial region. Since the lattice constant of the first semiconductor layer in the second layer is larger than the lattice constant of the second semiconductor layer, strain based on the difference in the lattice constant is induced in the second layer. Consequently, the second layer is bent so as to relax the strain. As the second layer is bent, the third layer on the second layer stands at a predetermined angle to the substrate.
The second layer is automatically bent so as to relax the strain caused by the difference in the lattice constant between the first semiconductor layer and the second semiconductor layer, whereby the third layer stands on the substrate. Therefore, the angle of the third layer can be easily and accurately controlled by adjusting the compositions and the thicknesses of the first semiconductor layer and the second semiconductor layer.
Consequently, a semiconductor device capable of accurately controlling the angle and the position of each of members constituting the standing structure as well as being easily comprised of a semiconductor layer is realized.
The method of fabricating the semiconductor device may further comprise the step of removing the third layer in the partial region. Consequently, the second layer can be easily bent at the partial region.
The step of forming the third layer may comprise the step of forming a third semiconductor layer having a lattice constant approximately equal to that of the first semiconductor layer in the second layer. In the case, the third layer is prevented from being curved, thereby forming a flat third layer standing on the substrate.
The step of forming the third layer may comprise the step of forming a third semiconductor layer having a lattice constant different from that of the first semiconductor layer in the second layer. In the case, the third layer is curved, thereby forming a third layer in the shape of a cylindrical shape standing on the substrate.
The predetermined region may include a plurality of regions, the step of removing the third layer, the second layer, and the first layer may comprise the step of removing the third layer, the second layer and the first layer in regions respectively surrounding the plurality of regions of the third layer, excluding partial regions, and the step of selectively removing the first layer may comprise the step of respectively removing the first layer in the plurality of regions and the partial regions, to bend at the respective partial regions the parts of the second layer in the plurality of regions.
In this case, the parts of the third layer stand on the substrate in the plurality of regions.
The step of selectively removing the first layer may further comprise the step of abutting the parts of the second layer, in the plurality of regions, bent at the respective partial regions or the parts of the third layer on the parts of the second layer against each other.
In this case, the plurality of parts of the second layer or the plurality of parts of the third layer are abutted against each other, whereby the angle of each of the parts of the third layer is defined. Accordingly, the angle of each of the parts of the third layer can be accurately set to a desired angle without precisely controlling the compositions and the thicknesses of the first semiconductor layer and the second semiconductor layer.
The step of selectively removing the first layer may further comprise the step of abutting the part of the second layer bent in at least one of the regions or the part of the third layer on the part of the second layer against another part of the second layer or another part of the third layer.
In this case, at least one part of the second layer or third layer is abutted against another part of the second layer or another part of the third layer, whereby the angle of the part of the third layer is defined. Accordingly, the angle of each of the parts of the third layer can be accurately set to a desired angle without precisely controlling the compositions and the thicknesses of the first semiconductor layer and the second semiconductor layer.
The step of forming the third layer may comprise the step of forming the third layer including a reflective film. In this case, a mirror standing on the substrate can be constructed.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.